1. Field of the Invention
The present invention relates to a wiring structure for a semiconductor device and a method for manufacturing the same.
2. Description of the Related Art
Aluminum having the second best conductivity after copper is used as a main material for wiring of a semiconductor device such as an integrated circuit (IC). However, aluminum wiring is vulnerable to breakage caused by electromigration. In order to increase the resistance against electromigration and to lengthen a life of the wiring, technologies are proposed to use an aluminum alloy such as Al--Cu and Al--Si--Cu or to introduce a stacked structure provided with the aluminum alloy as an upper layer and with a refractory metal layer composed of Ti, TiN, WSi or the like as a lower layer.
By forming the aluminum alloy layer, through the refractory metal layer, on an insulating layer on the semiconductor substrate such as Si, the aluminum alloy of high quality having few defects that may cause such electromigration and having a large grain diameter can be formed, and because the refractory layer used as the lower layer functions as a bypass for parts suffering from electromigration, the life of the wiring can be lengthened accordingly.
However, it was reported by M. Hosaka et al., in Proceedings of 36th International Reliability Physics Symposium (1998, P329) that, when the aluminum alloy layer is formed on the refractory metal layer described above, a compound layer composed of Al.sub.3 Ti is produced between the aluminum alloy layer and the refractory metal layer and an interface of compound layers acts as a diffusion path for aluminum. If such compound layers produced between aluminum and the refractory metal are formed in an ranged manner on the wiring region, it reduces remarkably the resistance against electromigration.